Thread rolling die



Set, le?,V 1941. A STOLL 2,256,269

.THREAD ROLLING DIE Original Filed Dec. 4, 1936 2 Sheets-Sheet 2 ALBERTSTOLL Patented Sept. 16, 1941 THREAD ROLLING DIE Albert Stoll, Detroit,Mich., assigner to Clare L. Brackett, Detroit, Mich.

Original applications Dece 114,259, and January 27,

Divided and this app Serial No. 157,195

4 Claims.

This invention relates to die apparatus for making' self-lockingscrew-threaded elements. Thel present application constitutes a divisionof my prior copending applications, Serial No. 114,259, filed December4, 1936, and Serial No. 122,629, filed January 27, 1937.

Self-locking screw-threaded elements, for example, valve tappetadjusting screws, are sometimes formed by providing two spaced threadedportions connected by a resilient portion whereof the threads of eachare relatively oiTset in an axial direction. By this construction,insertion of the element in the threaded bore of a receiving member,such as a valve tappet bore or other device, places the resilientconnecting portion under tension and locks the element in place againstaccidental displacement. The formation of screw-threaded elements ofthis character presents a difficult problem, particularly in theformation of the threads to produce the desired axial oiiset necessaryto secure self-locking.

An object of the present invention is to provide a novel die apparatusfor rolling offset screw threads on spaced threaded portions ofscrewthreaded elements,

Other objects and advantages will be apparent from the description.

While the present disclosure constitutes an exposition of embodiments bywhich the invention may be-reduced to practice, it is to be understoodthat the same may be varied as desired Within limits not inconsistentwith the scope of the invention as claimed.

In the accompanying drawings which form a part of thisspecification andwherein like characters of reference denote like parts throughout theseveral viewsz- Figure 1 is substantially an end elevation of a pair ofdies in thread forming engagement with a screw blank, the upper diebeing shown in section.

Figure 2 is an end elevation of one of the dies as provided with spacermeans for producing a desired thread offset, a portion being shown insection.

Figure 3 is a face plan view of a finished die as ready for use.

Figure 4 is an end elevation oi an alternative embodiment of a pair ofthread rolling dies for simultaneously rolling opposed pairs of blanks,as operatively engaged with such blanks.

Figure 5 is a fragmentary end elevation of one of the dies of Figure 4,illustrating by dotted line prolongation the offset of the adjacentthread forming portions.

mber 4, 1936 Serial No. 1937, Serial N0. 122,629;

lication August 3, 1937,

tik,

Figure 6 is a face plan View of one of the dies of Figure 4. l

Figure 7 is an end elevation of a further alteri-n a longitudinalvgroove 22aI in the meeting surface of die part 2) to maintain the dieparts in parallel relation to each other. rThe faces of the two partsare provided with Vinclined serrations 23 which produce the screw threadin a rolling operation.

As shown in Figure 1, the dies are employed in pairs to roll threads 24and 25 on a blank II,

headed as at I2, the threaded portions 24 and 25 being spaced axially ofthe blank lby a circumferentially undercut unthreaded portion havingslots I4 by which resiliency is imparted thereto,

the threads 24 and 25 being staggered relative to each other by virtueof an axial offsetting.

In order to produce the desired axial offset in the screw threadWhenrolled on the blank the serrations 23 of the. die part I9 areAoffset or staggered relative to the serrations 23 of the die part 20, asseen in Figure 3, so that when a blank is placed between a pair of suchdies the threads 24 on the screw are formed by the serrations of the dieparts I9 while'the threads25 on the leading end of the screw are formedbythe serrations of the die parts 2i).

The serrations 23, on the die parts` I9 and 2U are of the same depth andpitch so that the threads 24 and 25 on the finished screw will have thesame depth and pitch and will mesh with the threads of the element withwhich they engage in service, such as a tappet or socket having uniformand continuous threads. When the axially offset threads 24 and 25 engagesuch uniform and continuous threads the slotted resilient portion isdistorted and consequently forces the threads 24 and 25 into frictionallocking engagement with the threads of the tappet or socket.

As shown in Figure 2, the die parts I9 and 2D are assembled with spacersor shims 26 placed therebetween before the serrations 23 are cut intothe die faces, the thickness of such spacing means determining theamount of axial stagger or offset in the serrations of the two dieparts. The

serrations are then cut in the die faces in a single operation, as by ahob or the like, the method of cutting being disclosed in my copendingapplication entitledv Method of forming thread rolling dies, filedconcurrently herewith.

After the serrations 23 are formed the spacers 26 are removed and thedie partsI heat treated for hardening.- They are then assembled asshoWn'in Figures .1 and 3, without the spacers, which results in theserrations of die part I9 being staggered or oiset with respect to theserrations of die part 2U, as seen in Figure 3.

vIn the embodiment illustrated. in Figures 4; 5

and 6 each die is of integral construction, having a plurality of threadforming-face portionsZ'l,

V8 and 29 comprising zones-or Vbands disposed longitudinally o-f the diein parallel relation and spaced apart transversely of the die by definedareas 30, each of which is incapable of formative engagement with ablank being rolled. These areasSll are devoid of thread formingserrations and they may be provided in various ways as by gaps or planesurfaces. In the illustrated -embodiment they constitute gaps,preferably formed byflongitudinally groovingthe die'. faces to anappropriate depth. The gaps are so located that when blanks 3l areengaged between a pair of the dies,l as in lFigure 4, they register withthe undercut portions 32 ofthe blanks.

VThe thread forming serrations 27,- 28 and 29 on the respective die faceportions are each` oiset with respect to those of the adjacent .threadforming portion on the same die, so that on comformed with 4threads of`the same pitch diameter and pitch but the threads on one portion willbe Y set with respect to the thread forming .serrationsA pletion of athread rolling operation each blank f 'will have its threaded shankportions 33 and 34r offset axially of the blank relative to the threadsy 0n the other portion.

It should here be stated that dus to the onset' relationship of thethreaded portions 33 and 34 an axial stress will be set up inthe body ofthe screw kas it is threaded home in a female member, whereby thevreduced spacing portionV 32 will berplacedunder tension, thus providinga highly effective self-locking means. The degree of tension varies withthe amount of thread offset, s0

` thatY any desired tension may be obtained.

The method of forming the serrations in the ,portions 2l, 28 and 29,andof oisetting them, is

disclosed in my aforesaid concurrently led copending applicationentitled Method of forming thread rolling dies. l Also embodied in saidapplication is a disclosure of ,the method` employedvi'n securing thedesired thread forming offset in the alternative embodi` ments of diesshown in Figures 7 'and 8.

In the form illustrated'in Figure 7 the die 35 is formed-with a pair ofoverlapping closely adthe die faces. The slot 36 opens to the workingface of the die and extends nearly to its opposite Y face while the slot31 opens to the die face opposite its Working face and Vextends towardthe Working face. The slots are of equal length and extendlongitudinally of the die for its 4full length, opening to its ends. Inlthis embodiment'the slots provide the gaps separating the threadforming face portions 38 and 39 on which the thread forming serrationsare mutually oiset.

The die 40 shownin Figure 8 is similar to the die of vFigure '7, beinglikewise provided with slots 4l and 42 similar to the slots 36 and 31except that they are of greater width dueto the eX- panding action of..spacer members 43. engaged in the slots to cause a transverse expansionof the die body which resul-ts in offsetting the thread serrations onthe die face portions 44 and 45.

Having thus described the invention, what is claimed is:

1. A thread rolling die for yproducing axially offset threads on spacedportions of a blank, co'mprising a onefpiece die member having aplurelation, each saidvface portion having thread forming serrationsiofequal pitch and form offof thenext adjacent face portion.

2. A threadrolling dierfor producing axially oifset threads on spacedportions of a blank, comprisingfa one-piece die member having alongitudinal groove deining spaced parallel thread forming faceportions, each said face portion having thread forming serrations ofequal pitch and form oiset kwith respect to the thread formingserrations of the Vnext adjacent face portion.

`3. A thread rolling die for producing'axially offset threads on spacedportions of a blank, comprising a one-piece die member having aplurailty of thread forming face portions in spaced relation, Veach saidface portion having thread forming serrations ofequalrpitch and formoffset with'respect'to the thread forming serrations A of' the nextadjacent face portion, and means for adjusting the spacing of said faceYportions to vary the oifset of the thread forming serrations.

4. A thread rolling die for producing a selflocking screw with axiallyoffset threads, comprising a one-piece body having `a working face jprovided with thread forming Yserrations of equal pitch and formarranged as a plurality of spaced parallel zones, the body being cutaway ,between said zones to provide the spacing therefor, and

Vthe serrations of each zone `being oiset relative to theserrations ofthe adjacent/zones. l

ALBERT STOLL,

